The present application relates to a rod assembly for spinal stabilization.
WO 03/047442 A1 describes a damping element for use in spinal stabilization, the damping element has an outer spring, an inner spring and an adapter piece on either side of the outer and the inner spring. The inner spring abuts against the end of the adapters on both sides and is therefore not freely movable at one end.
US 2005/0085815 A1 describes a spinal stabilization rod comprising a core which is accommodated in a flexible tubular rod with tolerance in the axial direction.
US 2007/0049937 A1 describes a spinal stabilization rod which has a flexible tubular portion and a rigid end portion on either side of the flexible tubular portion and a core extending through the flexible portion and at least a part of the rigid end portions. The core can be fixed on one side and is freely movable on the other side.
US 2005/0154390 A1 describes a flexible element which has a core and two rod-like adapters being connectable to each end of the flexible element. The core does not extend into the adapter.
FIG. 1 shows a schematic representation of the spinal column together with bone anchoring elements 100 anchored, for example, in the pedicle of the vertebrae 101. Usually the bone anchoring elements are connected through a spinal stabilization rod which may be rigid (straight or curved) or flexible to some extent. As can be seen, the distance to be bridged by the rod between two bone anchoring elements is in the order of 25 to 30 mm in the higher thoracic region and decreases to 20 to 25 mm in the mid lumbar region until around 10 to 15 mm in the lower lumbar region. In specific clinical applications it may be necessary to stabilize different portions of the spine in a different manner, for example it may be necessary to use rigid as well as flexible stabilization at different locations. It may even be necessary to use a flexible stabilization with a different degree of flexibility at different locations of the spine, for example, on the right side and the left side. When considering the small distance between the bone anchoring elements in the lower lumbar part of the spine or in the cervical part of the spine, a compact shape and small dimensions of the stabilization rod or rod parts become necessary.
Based on the foregoing, there is a need to provide a rod assembly for spinal stabilization which can be used in a modular manner to allow a simple and versatile use, to provide a rod assembly which has small dimensions, and to provide a modular rod system for spinal stabilization.